[CASSANDRA-19812] We should throw exception when commitlog 's DiskAccessMode is direct but direct io is not support

• Type: Improvement
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 5.0.1, 5.1
• Component/s: Local/Commit Log
• Change Category: Operability
• Complexity: Low Hanging Fruit
• Platform: All

Source Control Link

https://github.com/apache/cassandra/commit/a84698753344e767145a38fe5b68722caa9b1254 https://github.com/apache/cassandra/commit/69a6dc61a89aac96b9f9a2a7aef958452e14384e

Test and Documentation Plan

ut

• Assignee: Maxwell Guo
• Reporter: Maxwell Guo

Authors

Maxwell Guo

Reviewers

Branimir Lambov, Stefan Miklosovic

• Created: 02/Aug/24 02:37
• Updated: 12/Oct/24 13:51
• Resolved: 16/Aug/24 07:14

Description

Looking into the code below :

private static DiskAccessMode resolveCommitLogWriteDiskAccessMode(DiskAccessMode providedDiskAccessMode)
    {
        boolean compressOrEncrypt = getCommitLogCompression() != null || (getEncryptionContext() != null && getEncryptionContext().isEnabled());
        boolean directIOSupported = false;
        try
        {
            directIOSupported = FileUtils.getBlockSize(new File(getCommitLogLocation())) > 0;
        }
        catch (RuntimeException e)
        {
            logger.warn("Unable to determine block size for commit log directory: {}", e.getMessage());
        }

        if (providedDiskAccessMode == DiskAccessMode.auto)
        {
            if (compressOrEncrypt)
                providedDiskAccessMode = DiskAccessMode.legacy;
            else
            {
                providedDiskAccessMode = directIOSupported && conf.disk_optimization_strategy == Config.DiskOptimizationStrategy.ssd ? DiskAccessMode.direct
                                                                                                                                     : DiskAccessMode.legacy;
            }
        }

        if (providedDiskAccessMode == DiskAccessMode.legacy)
        {
            providedDiskAccessMode = compressOrEncrypt ? DiskAccessMode.standard : DiskAccessMode.mmap;
        }

        return providedDiskAccessMode;
    }

We should throw exception when user set the DiskAccessMode to direct for commitlog but the directIOSupported return false after the judgement of "FileUtils.getBlockSize(new File(getCommitLogLocation())) > 0;" instead of waiting for the system to start and accepting reads and writes.